1. Field
Apparatuses and methods consistent with exemplary embodiments relate to holographic 3-dimensional (3D) image display apparatuses and illumination units for the same, and more particularly, to illumination units having optical systems with improved aberration and holographic 3D display apparatuses including the same.
2. Description of the Related Art
Nowadays, in various fields, such as movies, games, advertising, education, the military, and the like, 3-dimensional (3D) image display apparatuses are in great demand to produce images realistically and effectively. Accordingly, various technologies for displaying 3D images have been developed, and various 3D image display apparatuses are already used.
3D image display apparatuses, for example, are categorized as glasses apparatuses and a glasses-free apparatuses. In addition, glasses apparatuses are categorized as polarized glasses apparatuses and shutter glasses apparatuses. A glasses-free apparatus may use stereoscopy, and may be a lenticular apparatus which uses a plurality of cylindrical lens arrays or a parallax barrier apparatus including a plurality of barriers and openings. However, the above-described apparatuses based on stereoscopy take advantage of the binocular parallax between the eyes, and thus, there are limitations in increasing the number of viewpoints, and viewers may also feel fatigued due to a mismatch of a stereoscopic depth recognized by the brain and the focus of the eyes. In addition, these apparatuses provide only horizontal parallax and not vertical parallax.
As a 3D image display apparatus capable of matching the stereoscopic depth recognized by the brain and the focus of the eyes and providing full parallax, a holographic apparatus and an integrated image apparatus have been suggested. A holographic image apparatus allows a signal beam having an image signal to interfere with a reference beam. An integrated image apparatus displays a 3D image by using a fly-eye lens, which includes an array of a plurality of micro lenses.
A holographic 3D image display apparatus generally includes an illumination unit and a spatial light modulator (SLM). The illumination unit plays provides a light beam having a controlled phase and amplitude to the SLM. The illumination unit may include a coherent light source, such as a laser, a spatial filter, a projection optical system, and the like. The projection optical system may include a lens or a mirror. In order to provide a light beam emitted from a light source which uniformly illuminates the entire region of the SLM, a size of the lens or the mirror of the illumination unit may be similar to or greater than that of the SLM. The SLM performs phase modulation or amplitude modulation on a light beam incident from the illumination unit, and, by using light diffraction and interference, allows a stereoscopic image to be formed at a predetermined position in space.